1. Field of the Invention
The present invention relates to a shoe press, in particular a shoe press for a paper machine, including at least one roll consisting of a flexible roll sleeve that circulates around a stationary carrier and is rotatably mounted on the carrier at each of its two axial end areas over a support device, and at least one shoe that has a support surface for the interior side of the roll sleeve.
2. Discussion of Background Information
In shoe presses of this type, a flexible roll sleeve is usually pressed against a rigid mating roll by a press shoe which curves inward in a concave manner. A press opening is thus created between the press roll and the mating roll that has a certain length, which is also referred to as that press zone length, in the feed direction of the pressed material. The longer the press zone, the greater the press impulse which is applied, for a given contact pressure of the press shoe onto the pressed material. Therefore, the contact pressure of the press shoe can differ across the press zone in the feed direction of the pressed material, thereby exhibiting pressure gradients.
When paper is the material to be pressed, for example, increasing demands are placed on its dryness content, smoothness and volume, among other things. A goal, therefore, is to increase the press impulse. At the same time, however, the maximum pressure and the pressure gradient in the press opening should be kept at a minimum.
In order to achieve this, extensions of the press zone, i.e. of the press shoe, can be considered. These are limited to the length of approximately 300 mm which is achievable today, however, since increased shoe length causes the dipping depth of the flexible roll sleeve to correspondingly be increased, because of the concave supporting surface of the press shoe which matches the surface of the mating roll. Increased dipping of the flexible roll sleeve has the disadvantage, among other things, of strong roll sleeve bending at the inlet and outlet areas of the press opening. Deformations in the edge areas of the press shoe are particularly strong and critical, since a transition in the axial direction to a circular cylindrical form, influenced by the radial support of the roll sleeve, also occurs at this location.